Drug Testing - The Definitive Guide
DETECTION TIMES
Drug tests detect drugs as well as metabolites. Metabolites are the byproducts of a substance after it has run through your system. To determine whether you will pass or not, it is important to know how much of the illicit metabolites are in your urine and how much is tested for. Usually marijuana tests will have a cutoff of 50ng/mL. That is the standard in the industry. You might run across the occasional test that has a lower cutoff level (Level of Detection, [LOD]), Home testing can tell you whether your level at the time of the test is above or below the 50ng/mL level, but it will not tell you the exact level of THC metabolites in your system.
Half-life of TetraHydraCannabinol
The half life of THC concentration ranges between about 1 to 10 days. There is way too much variation to even approximate how long THC will be detected in the urine of an individual. Infrequent users with a fast metabolism will have the shortest detection time. Frequent or chronic users with a slow metabolism will have long detection times. The only way to estimate a detection time is to consider the lower and upper bounds (3-50 days), and decide based on the factors outlined here.
Note: Detection times vary depending on drug potency, tolerance, patient's condition, fluid intake at time of test, and method and frequency of marijuana use. These are general guidelines only.
If you are currently using marijuana and know you have a test coming up, stop using immediately. The longer you abstain, the better your chances of passing a test will be.
Other factors determining degree of intoxication include metabolism, tolerance, frequency of intake, fluid intake, amount of marijuana, and length of time you've been a user. If you use marijuana on rare occasions, your urine may be clean of metabolites in less than a week. There is a common and strange phenomena that occurs with chronic users. You would expect a chronic user to have the longest detection time and the smallest chance of passing. This is not always the case. A chronic user with a high tolerance may eliminate drugs as fast as an occasional user. Chronic users have tested negative after a week long binge. Fat tissue also makes a huge difference. Skinny users not only have a faster metabolism (usually), but also lack storage for THC metabolites. The more fat a person has, the more THC metabolites will be stored in the body, the longer detection time for a user.
"How long will it take ‘til I test clean?" This is the single most frequently asked question. It is impossible for anyone to estimate the time it would take for someone to test clean. The best thing you can do for yourself is test yourself after you’ve stopped smoking pot. Test about twice weekly until your first urine of the day tests clean. That is how long it takes YOU to clean out after your normal smoking habits. Even that will vary depending on your level of usage prior to abstaining and level of activity while testing yourself. Don’t let your best friends brother’s girlfriend’s cousin’s experience be your guide. Every BODY is different.
Computer programs, charts and graphs are virtually useless in determining how long it will take YOU, the individual, to test negative.
Positive (defined)
50 nanograms of THC metabolites per milliliter defines a "presumptive positive" by most laboratories and instant tests. This value was originally 20 ng/mL, but too many false positives resulted. So the level was raised to 100 ng/mL to reduce false positives. As of January 1995, the threshold was lowered back down to 50 ng/mL because drinking excessive water could easily bring the level of metabolites in the urine below 100 ng/mL. Some employers may use a lower cutoff, but that is rare. If a specimen screens non-negative for THC (anything other than negative or fails an integrity test), the specimen is then sent through a Gas Chromatograph / Mass Spectrometer (GC/MS) for the specific metabolite tripping the immunoassay screening. This level is set at 15 ng/mL for that one specific metabolite.
Passive smoke and positives
"If you heard that secondhand marijuana smoke can cause you to fail your drug test the next day, it might be true. It is possible that secondhand marijuana smoke will raise someone to the 50 ng/mL level; however, *EXTREME* exposure is required. For instance, a closed car full of pot smokers might cause someone exposed to that quantity of smoke to test positive in a drug test the next day; provided that they are sealed in the car for a while (a few hours). Non-smokers are safe in a ventilated area such as an average living room or garage where partygoers are smoking pot.
